if you have NEVER used a computer before, then fine, get a mac, they are easier to learn the basics on.
If you have used a windows machine, go for a PC, the extra expense on a mac just isnt worth it for 95% of users.
the only advantage a MAC has over a PC is you can put rediculous amounts of ram in them if you are doing LOTs of hi usage tasks, ie video editing, special effects etc.
For most, the 4Gb of ram a normal PC can use is fine (Ok, just for the picky its 3.2Gb)
in general X number of ££ will give you a better PC than MAC
and contrary to belief, there IS a risk, and a growing one of security issues with macs, the more users there is, the more this risk is going to grow.
As long as you take normal precautions, updates, viruses and abit of common sense it is perfectly safe.